1. Field of the Invention
The present invention relates to a diathermic snare which sucks a diseased mucous membrane into an almost cylindrical cap that is mounted on the distal end of an inserting section of an endoscope to be brought into a polyp and then removing the polyp, a medical instrument system using the snare, and a method of assembling the medical instrument system.
2. Description of the Related Art
Recently, endoscopic demucosation has widely been performed for early esophagus cancer and gastric cancer. In this demucosation, an operator removes a diseased mucous membrane using an endoscope without opening up the abdomen. One method of the demucosation is disclosed in Jpn. UM Appln. KOKAI Publication No. 6-75402 (patent publication 1) and Jpn. Pat. Appln. KOKAI Publication No. 2001-275933 (patent publication 2). These publications disclose using an endoscope and a diathermic snare in combination. An almost cylindrical hood is mounted on the distal end of an inserting section of the endoscope. The hood has a flange-shaped projection (lug) that projects inward from the inner surface of the distal end of the hood.
The diathermic snare includes an elongated flexible sheath and an operating wire. The operating wire is inserted in the sheath such that it can move forward and backward. A snare wire is connected to the distal end of the operating wire. The snare wire has a loop section that expands almost circularly or elliptically. The loop section projects from the sheath and retracts thereinto as the operating wire moves forward and backward. When the operating wire is pulled toward an operator, the snare wire is pulled and stored in the sheath with its loop section retracted. When the operating wire is pushed forward, the snare wire is projected out of the sheath. The loop section expands like a loop by its own elasticity.
When the diathermic snare is used, it is inserted into a channel of the endoscope. The distal end of the snare projects forward from the channel of the endoscope. In this state, the snare wire projects out of the sheath. The loop section therefore expands like a loop by its own elasticity. The loop section is formed along the flange-shaped projection inside the hood. After that, the diseased mucous membrane to be treated is sucked into the hood and then projected like a polyp. The polyp-like mucous membrane is strangulated at its root by the loop section of the snare and then removed by the passage of power through the snare.
Jpn. Pat. Appln. KOKAI Publication No. 2002-45369 (patent publication 3) discloses a soft tube that is coupled to a hood as disclosed in patent publications 1 and 2. The distal end of the soft tube is connected to a communication opening of the hood to communicate with the inside of the hood. A diathermic snare is inserted into the soft tube. The snare projects a snare wire out of the sheath thereof. Thus, the loop section of the snare wire is expanded like a loop and formed along a flange-shaped projection in the hood. The loop section is then fixed in the hood by an adhesive.
The above method employs a known diathermic snare that is disclosed in Jpn. UM Appln. KOKAI Publication No. 56-160516 (patent publication 4) and Jpn. UM Appln. KOKOKU Publication No. 6-9623 (patent publication 5). The diathermic snare of patent publication 4 has a snare loop that is formed asymmetrically because only one side of the loop is movable. The diathermic snare of patent publication 5 has a snare loop that is formed symmetrically, e.g., elliptically.